Fishing and general state of fisheries

This is the first post in the topic Impacts of the fishing, whose goal is to expose the impact of fisheries in the sea populations and them ecosystems.

 

Fishing consists on the exploitation of the aquatic populations that exsists naturaly. Since 1950, it has been observed an increase of the natural captures until 1990 due to the incorporation of motors and sonars in the ships. As of 1990, the capture are around 90 million tonnes. Nowadays, the fishing pressure is so high that the fisheries tend to collapse because the adults cannot produce enough juvenile fishes. The following picture shows the evolution of the natural captures (blue) and the evolution of aquaculture production (green) (FAO).

evolució pesca

The captures of the fisheries have different components. On one side, the capture of the species of interest (goal species) and, on the other side, the other species with no interest (bycatch). Bycatch can be divided into species with low value or discards. Discards consists on species captured unintentionally because they economic value is non-existent, species legally protect or with a bad appearance. Fishing by trawling discards 40% of the captures.

A fishing stock consists on a population or a piece of it that is exploited as a whole. Depending on the exploitation of the stocks, these can be non-fully exploited (blue), when the fishing pressure don’t affect the population; overexploited (red), when the juvenile fishes aren’t enough to recover the adult population; or fully exploited (green), when the stock tends to collapse.

stocks

A 10-times reduction on the fishing resources of the continental shelf in just a century has been reported (Christensen et al. 2004), and a reduction too in the resources of the abyssal plain (Devine et al. 2006) and the open sea.

The climate change and the fishing are the main factors that impact the sea. The effects of the fishing take place in the organisms and ecosystems.

 

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